Multilayer coating and process for its production

ABSTRACT

The invention provides a cured multilayer coating having improved properties and a process for the production of said cured multilayer coating. In particular, the invention provides a method of making a cured multilayer coating which comprises applying by electrophoretic deposition a first curable coating composition (I) to a substrate, the first curable coating composition (I) comprising (a) a compound comprising one or more active hydrogen-containing groups, and (b) a curing agent comprising one or more groups reactive with active hydrogen-containing groups, applying a second curable coating composition (II) to the applied first curable coating composition (I) while the applied first curable coating composition is in an uncured state, the second curable composition (II) comprising (a) a compound comprising one or more active hydrogen-containing groups, and (b) a curing agent comprising one or more groups reactive with active hydrogen-containing groups, and subjecting the applied first and second curable coating compositions to conditions sufficient to cause curing of both compositions, wherein curing agent (I)(b) is reactive with compound (II)(a) and curing agent (II)(b) is reactive with compound (I)(a) under the applied cure conditions. The invention further provides a multilayer film composition comprising (I) a first film resulting from the curing of a first curable coating composition (I) comprising (a) a compound comprising one or more active hydrogen-containing groups, and (b) a curing agent comprising one or more groups reactive with active hydrogen-containing groups, and (II) a second film resulting from the curing of a a second curable coating composition (II) comprising (a) a compound comprising one or more active hydrogen-containing groups, and (b) a curing agent comprising one or more groups reactive with active hydrogen-containing groups, wherein (1.) the second curable coating composition (II) was applied to the first curable coating composition (I) while the first curable coating composition (I) was in an uncured state, and (2.) curing agent (I)(b) was reactive with compound (II)(a) and curing agent (II)(b) was reactive with compound (I)(a) in the conditions in which the first and second curable coating compositions where cured.

FIELD OF THE INVENTION

[0001] The invention relates to multilayer films or cured multilayercoatings and a process for the production of such. More particularly,the invention relates to multilayer films having a first layer appliedby electrophoretic deposition processes and a second layer appliedthereto wet-on-wet, followed by a joint and simultaneous curing of thefirst and second layers.

BACKGROUND OF THE INVENTION

[0002] Automotive manufacturers have traditionally relied uponelectrophoretically deposited coatings, both cathodic and anodic, forsignificant protection against corrosion of the underlying metalautomotive body. “Electrocoat” as used herein may refer to both curablecoating compositions used in electrophoretic deposition processes and tocured coating films obtained from the curing of coating compositionsapplied by electrophoretic deposition processes.

[0003] During electrodeposition, an ionically-charged polymer having arelatively low molecular weight is deposited onto a conductive substrateby submerging the substrate in an electrocoat bath having dispersedtherein the charged resin, and applying an electrical potential betweenthe substrate and a pole of opposite charge, usually a stainless steelelectrode. This produces a relatively soft coating of low molecularweight on the substrate. Traditionally, this coating is converted to ahard high molecular weight coating by curing or crosslinking of theresin, usually upon exposure to elevated temperatures prior to anyfurther application of subsequent coating layers.

[0004] However, automotive manufacturers have long desired to eitherlower the temperature required to cure the electrodeposited coating orto eliminate such a separate curing step all together. In particular,automotive manufacturers would like to use electrodeposited coatings asthe first part of a wet-on-wet process. It will be appreciated that“wet-on-wet” typically refers to a coating application process whereinsubsequent coatings are applied directly to a substantially uncuredpreviously applied coating. The two or more uncured coatings are thenjointly baked or cured. “Wet-on-wet” may encompass processes wherein thefirst coating is subjected to conditions which eliminate solvent and/orreduce the volume of the first film, but stop short of complete cure orcrosslinking.

[0005] The elimination of the separate bake step following applicationof a traditional electrocoat composition would result in significantenergy and space savings, due to the elimination of an entire bakingoven.

[0006] Thus, it is desirable to provide a multilayer film compositionhaving optimum performance properties which is at least partiallyobtained through the application of a curable basecoat, primer or sealercoating directly onto a substantially uncured or “wet” previouslyelectrodeposited coating, followed by the joint or simultaneous curingof both the wet electrodeposited coating and the wet basecoat, primer orsealer coating.

[0007] The prior art has long attempted to provide methods to make suchcured multilayer coating or film compositions and/or coatingcompositions for use in said methods.

[0008] For example, U.S. Pat. No. 3,998,716, Masar et al., disclosesthermosetting coatings wherein multiple coats of thermosetting organiccoating material, including a topcoat of powder paint are cured byemploying a single baking step.

[0009] U.S. Pat. No. 5,507,928, Böhmert et al., discloses a process forthe production of multi-layer lacquer coatings by electrophoreticdeposition of a first coating layer of a first aqueous coatingcomposition onto an electrically conductive substrate, application of asecond coating layer based on a second, powder coating composition andjoint baking of the coating layers so obtained, which process ischaracterized in that a powder coating composition is used for thesecond layer which is based on binders which contain no diene-basedpolymer units, wherein the coating composition is selected such that theminimum baking temperature range of the second coating layer is abovethat of the first coating layer or overlaps with this range in such amanner that the lower limit of the range of the second coating layer isabove the lower limit of the range of the first coating layer.

[0010] However, the use of a powder coating composition as the secondapplied coating is not always desirable.

[0011] U.S. Pat. No. 5,376,457, Smith, discloses a process of applying afinish to an electrically conductive vehicle body wherein anelectrocoated coating is dehydrated to a state of sufficient dryness topermit spray application of a water-based primer while maintaining thecoat cool enough to avoid fusing the electrocoat coating. Theelectrocoat and subsequently spray applied water-based primer are thenconcurrently baked so as to “fuse both of them”.

[0012] In U.S. Pat. No. 5,869,198, Erne et al., a process is disclosedfor the multi-layer coating of electrically conductive substrates by theelectrophoretic deposition of a first coating layer comprising anelectrophoretic deposition of a first coating layer comprising anelectrophoretically depositable aqueous coating medium, and thesubsquent application of further coating layers, which is characterizedin that a second coating layer comprising a first color- and/or effectimparting base lacquer coating medium is applied wet-into-wet to thefirst coating obtained by electrophoretic deposition, and the first andsecond coating layers thus obtained are jointly stoved, whereupon athird coating layer comprising a second color- and/or effect-impartingbase lacquer coating medium is applied and a fourth coating layercomprising a clear lacquer coating medium is applied wet-into-wetthereto and the third and fourth coating layers are stoved jointly,wherein the total dry coat thickness (the sum of the coat thickenesses)of the second and third coating layers produced from the base lacquercoating media is between 15 and 40 μm, and the proportion of the secondcoating layer is between 20 and 50% of the total dry coat thickness ofthe second and third coating layers.

[0013] U.S. Pat. No. 4,619,746, Delaney et al., discloses a process forapplying a non-electrophoretic top-coating over an electrophoreticallyapplied base coating and curing the composite coating by employing asingle curing step. Isocyanates, and most preferably blockedisocyanates, are the preferred curing agent for the electrophoreticallyapplied basecoat and the non-electrophoretic topcoating composition.

[0014] However, the use of isocyanate curing agents, particularlyblocked isocyanate curing agents, is no longer favored, especially inelectrocoat compositions. Blocked polyisocyanates require hightemperatures (e.g., 176° C. or more) to unblock and begin the curingreaction. The resulting coating can also be susceptible to yellowing.Moreover, the volatile blocking agents released during cure can causeother deleterious effects on various coating properties, as well asincreasing VOC. In addition, use of some of the volatile blocking agentsmay give rise to environmental concerns. Finally, the volatile blockingagents account for significant and disadvantageous weight loss uponcrosslinking.

[0015] U.S. Pat. No. 5,389,406, Doebler et al., describes a process forproducing multilayer coatings in which a first coating layer of a firstaqueous coating medium is applied to an electrically conductingsubstrate by electrophoretic deposition, is provided wet-in-wet with asecond coating layer of a second aqueous coating medium, followed byjoint stoving, wherein a coating medium based on one or more vehiclesstabilized by ionic groups and which crosslink on stoving with theformation of urethane groups is used for the second coating layer, andthe coating media are selected so that the maximum pigment/vehicleweight ratio of the first coating medium is 1:1, that the ratio of thepigment/vehicle weight ratio of the first coating medium to that of thesecond coating medium is up to 1.8, and the minimum stoving temperatureinterval of the second coating layer is above that of the first coatinglayer or overlaps the latter so that the lower limit of the interval forthe second coating layer is above the lower limit of the interval forthe first coating layer.

[0016] However, none of these prior art patents have resolved the abovenoted problems. In particular, the prior art has failed to providedcured multilayer films having the desired performance properties.

[0017] It is believed that the failings of the prior art areattributable at least in part to the prior art's failure to recognizethe underlying factors addressed by the instant invention. Inparticular, the prior art has failed to address the fact that cationicelectrocoat compositions and acid catalyzed aminoplast cured basecoats,sealers and/or primers are the coatings of choice for many automotivemanufacturers and suppliers. However, the wet-on-wet application of theacidity catalyzed aminoplast based coatings onto the highly basiccationic amine functional resins has been found to result in anincompatible interrelationship. While not wishing to bound to aparticular theory, it is believed that the basic amines of the cationiccoatings inhibit the cure of subsquently applied aminoplast curedcoatings. The instant invention recognizes this aspect and thus providesunexpected advanatages.

[0018] It is an object of the invention to provide a multilayer filmcomposition having optimum performance properties which is at leastpartially obtained through the application of a curable basecoat, primeror sealer coating directly onto a substantially uncured or “wet”previously electrodeposited coating, followed by the joint orsimultaneous curing of both the wet electrodeposited coating and the wetbasecoat, primer or sealer coating.

[0019] It is another object of the invention to provide a commerciallyadvantageous method of making a cured multilayer film compositionwherein a second coating layer is applied wet-on-wet to a previouslyapplied electrophoretically deposited first coating layer and bothlayers are jointly cured to provide a cured film.

[0020] It is a further object of the invention to provide such a methodwhich does not rely on the use of isocyanates or blocked isocyanates andwhich can utilize commerically desirable cationic electrocoatcompositions as well as commercially desirable aminoplast curedbasecoats, sealers and/or primers.

[0021] Finally, it is an object of the invention to provide curedmultilayer coating compositions (also referred to as multilayer filmsherein) which are produced by the methods of the invention.

SUMMARY OF THE INVENTION

[0022] It has unexpectedly been found that the foregoing objects may beachieved with the method of the invention. Accordingly, the inventionprovides a method of making a cured multilayer coating, the methodcomprising applying by electrophoretic deposition a first curablecoating composition (I) to a substrate, the first curable coatingcomposition (I) comprising, (a) a compound comprising one or more activehydrogen-containing groups, and (b) a curing agent comprising one ormore groups reactive with active hydrogen-containing groups, applying asecond curable coating composition (II) to the applied first curablecoating composition (I) while the applied first curable coatingcomposition is in an uncured state, the second curable composition (II)comprising (a) a compound comprising one or more activehydrogen-containing groups, and (b) a curing agent comprising one ormore groups reactive with active hydrogen-containing groups, andsubjecting the applied first and second curable coating compositions toconditions sufficient to cause curing of both compositions, whereincuring agent (I)(b) is reactive with compound (II)(a) and curing agent(II)(b) is reactive with compound (I)(a) under the applied cureconditions.

[0023] The invention further provides a multilayer film compositioncomprising (I) a first film resulting from the curing of a first curablecoating composition (I) comprising (a) a compound comprising one or moreactive hydrogen-containing groups, and (b) a curing agent comprising oneor more groups reactive with active hydrogen-containing groups, and (II)a second film resulting from the curing of a a second curable coatingcomposition (II) comprising (a) a compound comprising one or more activehydrogen-containing groups, and (b) a curing agent comprising one ormore groups reactive with active hydrogen-containing groups, wherein(1.) the second curable coating composition (II) was applied to thefirst curable coating composition (I) while the first curable coatingcomposition (I) was in an uncured state, and (2.) curing agent (I)(b)was reactive with compound (II)(a) and curing agent (II)(b) was reactivewith compound (I)(a) in the conditions in which the first and secondcurable coating compositions where cured.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] The instant invention requires the use of a first curable coatingcomposition (I) and a second curable coating composition (II). Bothcoating compositions will comprise a compound (a) comprising one or moreactive hydrogen-containing groups, and a curing agent (b) comprising oneor more groups reactive with the active hydrogen-containing groups ofthe compounds (I)(a) and (II)(a).

[0025] It is a necessary aspect of the instant invention that curingagent (I)(b) be reactive with compound (II)(a) under the cure conditionswhich are applied to jointly cure curable coating composition (I) andcurable coating composition (II). It is also necessary that curing agent(II)(b) be reactive with compound (I)(a) under the same applied cureconditions. While it is not necessary that curing agent (I)(b) andcuring agent (II)(b) be identical, it is preferred that both curingagents operate using the same curing mechanism. As used herein, the term“curing mechanism” refers to the addition or condensation reactionbetween components (a) and (b) that results in a crosslinked network.Put another way, curing agent (I) must be such that it would curecurable coating composition (II) under the applied cure conditions, ifit were substitued in place of curing agent (II). Similarly, curingagent (II) must be such that it would cure curable coating composition(I) under the applied cure conditions, if it were substituted in placeof curing agent (I).

[0026] In a preferred embodiment, the curable coating compositions (I)and (II) will both further comprise a catalyst (c) for the reactionbetween reactive compound (a) and curing agent (b), wherein the catalyst(I)(c) is also a catalyst for the reaction between reactive compound(II)(a) and curing agent (II)(b), and the catalyst (II)(c) is also acatalyst for the reaction between reactive compound (I)(a) and curingagent (I)(b). The phrase “is also a catalyst for” is meant to indicatethat said material changes the speed of the noted reaction as well asthe reaction for which it is originally intended to be catalytic, but ispresent in its original concentration at the end of the reaction. (Itwill be appreciated that concentration of catalyst refers only tounblocked catalyst in the case of blocked catalysts.) That is, catalyst(I)(a) will, under the applied curing conditions, change the speed ofthe reaction (I)(a)+(I)(b), as well as change the speed of the reaction(II)(a)+(II)(b). Likewise, catalyst (II)(c) will, under the appliedcuring conditions, change the speed of the reaction (II)(a)+(I)(b), aswell as change the speed of the reaction (I)(a)+(I)(b).

[0027] In a most preferred embodiment, the curing agents (I)(b) and(II)(b) will be the same and will not be a polyisocyanate.

[0028] These and other aspects of the invention will be described indetail below.

[0029] Per the method of the invention, the curable coating composition(I) must be suitable for application by an electrophoretic depositionprocess. Suitable coating compositions (I) may be either anodic orcathodic/cationic coating compositions. It will be appreciated thatcured films produced by such electrophoretic deposition processes arereferred to as electrocoat coatings or e-coat and are typically used asa first applied primer coat for protection against corrosion.

[0030] Curable coating composition (I) will comprise a compound (a)comprising one or more active hydrogen groups and at least one or moreionic groups or groups convertible to ionic groups. The ionic groups orgroups which can be converted to ionic groups may be anionic groups orgroups which can be converted into anionic groups, e.g. acidic groupssuch as —COOH groups, or cationic groups or groups which can beconverted into cationic groups, e.g. basic groups such as amino groupsand ammonium groups such as quaternary ammonium groups, or phosphoniumand/or sulphonium groups. Basic groups which contain nitrogen areparticularly preferred. These groups may be present in quaternised form,or are at least partially converted into ionic groups with a customarynuetralising agent such as an acid, e.g. an organic monocarboxylic acid,such as formic acid or acetic acid for example.

[0031] Examples of suitable compounds (a) for use in anodic curablecoating compositions (I) include polymers which are based on polyesters,acrylics, vinyl, epoxy, polyurethane, alkyds, mixtures thereof, and thelike. Thus, the one or more active hydrogen groups for suitable anodiccompounds (a) may generally be selected from the groups consisting ofcarboxylic acid, hydroxyl, carbamate, isocyanate, amine, epoxy,acrylate, vinyl, acetoacetate, mixtures thereof and the like, withhydroxyl, carbamate and mixtures thereof being preferred and hydroxyl,primary carbamate and mixtures thereof being most preferred.

[0032] Illustrative examples of suitable compounds (a) for use in anodiccoating compositions (I) will have a weight average molecular weight inthe range of about 300 to 100,00, preferably from 10,000 to 60,000.Weight average molcular weight can be determined by the GPC method usinga polystyrene standard. Suitable compounds (a) may also be characterizedby an acid number in the range of 20 to 300 mg KOH/g for example,preferably from 20 to 80, most preferably from 30 to 50.

[0033] Anodic compounds (a) will typically comprise one or more,preferably a plurality of, ionic groups which are acidic such as —COOH,—SO₃H and/or PO₃H₂ groups, with —COOH groups being most preferred. Theanodic compounds (a) can be converted into the aqueous phase afterneutralisation of at least part of the acidic groups. Neutralisationpreferably occurs with amines, especially tertiary amines or alkanolamines and most preferably with teritary alkanol amines such as dimethylethanol amine.

[0034] Preferred compounds (a) for use in anodic coating compositions(I) are those which are obtained through the copolymerization of one ormore monomers selected from the group consisting of alkyl and hydroxyalkyl esters of unsaturated organic acids, ethylencially unsaturatedmonomers, unsaturated organic acids and mixtures thereof. Examples ofsuitable alkyl and hydroxy alkyl esters of (meth)acrylic acid includeethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, butylmethyacrylate, isodecyl methyacrylate, hydroxyethyl methacrylate,hydroxypropyl methacrylate, and the like. Examples of suitableethylenically unsaturated monomers include unsaturated m-tetramethylxylene isocyanate (sold by American Cyanamid as TMI®), styrene, vinyltoluene, alpha methyl styrene and the like. Examples of suitableunsaturated organic acids include acrylic acid, methacrylic acid,crotoic acid, vinylacetate acid, tiglic acid, 3,3-dimethylacrylic acid,trans-2-pentenoic acid, 4-pentenoic acid, trans-2-methyl-2-pentenoicacid, 6-heptanoic acid, 2-octenoic acid, and the like. Preferredunsaturated organic acids include acrylic acid, methacrylic acid, andmixtures thereof.

[0035] A most preferred anodic compound (a) is that disclosed in pendingU.S. patent application, Ser. No. 09/217,557, entitled “AnodicElectrocoat having a Carbamate Functional Resin”, all of which is herebyincorporated by reference. Such an anodic compound (a) will have atleast one carbamate functional group appended to a polymer backbone,preferably a plurality of pendant carbamate functional groups.

[0036] Illustrative examples of the most preferred anodic compounds (a)suitable for use in the instant invention can be prepared in a varietyof ways. One way to prepare such polymers is to prepare an acrylicmonomer having a carbamate functionality in the ester portion of themonomer. Such monomers are well-known in the art and are described, forexample in U.S. Pat. Nos. 3,479,328, 3,674,838, 4,126,747, 4,279,833,and 4,340,497, the disclosures of which are incorporated herein byreference. One method of synthesis involves reaction of a hydroxy esterwith urea to form the carbamyloxy carboxylate (i.e., carbamate-modifiedacrylic). Another method of synthesis reacts an α,β-unsaturated acidester with a hydroxy carbamate ester to form the carbamyloxycarboxylate. Yet another technique involves formation of a hydroxyalkylcarbamate by reacting a primary or secondary amine or diamine with acyclic carbonate such as ethylene carbonate. The hydroxyl group on thehydroxyalkyl carbamate is then esterified by reaction with acrylic ormethacrylic acid to form the monomer. Other methods of preparingcarbamate-modified acrylic monomers are described in the art, and can beutilized as well. The acrylic monomer can then be polymerized along withother ethylenically-unsaturated monomers, if desired, by techniqueswell-known in the art. However, such ethylenically unsaturated monomersmust comprise at least one monomer having a pendant carboxylic acidgroup.

[0037] For example, preferred methods of preparing illustrative examplesof the anodic compound (a) most preferred for use in the instantinvention include the following. One or more carbamate functionalmonomers such as 2-carbamate ethyl methyacrylate (CEMA) may becopolymerized with two or more monomers such as an unsaturated organicacid and a alkyl ester of an unsaturated organic acid in the presence ofa suitable initiator such as an azo or peroxide initiator. Othersuitable carbamate functional monomers include those described above.Suitable unsaturated organic acids will be of the formulas R¹R²═R³COOHor R¹R²═R³R⁴COOH, where R¹, R², R³, and R⁴ may be the same or differentand are selected from the group consisting of H, alkyl groups of from 2to 12 carbons, and mixtures thereof. Examples of suitable unsaturatedorganic acids include acrylic acid, methacrylic acid, crotoic acid,vinylacetate acid, tiglic acid, 3,3-dimethylacrylic acid,trans-2-pentenoic acid, 4-pentenoic acid, trans-2-methyl-2-pentenoicacid, 6-heptanoic acid, 2-octenoic acid, and the like. Preferredunsaturated organic acids include acrylic acid, methacrylic acid, andmixtures thereof. Examples of suitable alkyl esters of unsaturatedorganic acid include ethyl acrylate, butyl acrylate, 2-ethylhexylacrylate, butyl methyacrylate, isodecyl methyacrylate, hydroxyethylmethacrylate, hydroxypropyl methacrylate, and the like. Preferred alkylesters are nonhydroxy functional esters such as butyl acrylate andbutylmethacrylate. Other ethylenically unsaturated monomers such asstyrene may be also used.

[0038] In another reaction scheme, an isocyanate functional monomer suchas unsaturated m-tetramethyl xylene isocyanate (sold by AmericanCyanamid as TMI®) can be copolymerized with monomers such as alkylesters, such as described immediately above, and unsaturated monomers,such as styrene, to produce an isocyanate functional polymer. Therequired carboxylic acid functionality and carbamate functionality canthen be grafted onto the isocyanate functional polymer by a two-stagereaction having a first stage using a carbamate functional monomer suchas hydroxypropyl carbamate followed by a second stage using a carboxylicacid of the formula HO—(R)—COOH or an amine salt of the formulaHO—(R)—COOH⁺NR₃, wherein R is an alkyl group of from 1 to 12 carbons,preferably from 2 to 8 carbons.

[0039] Alternatively, one or more carbamate functional monomers may bereacted with an isocyanate functional monomer such as an unsaturatedm-tetramethyl xylene isocyanate to produce a carbamate functionalmonomer. Additional isocyanate monomer may be added to introduceisocyanate functionality in the monomer mixture. After polymerizing theone or more monomers, the required pendant carboxylic acid functionalitycan be grafted onto the polymer backbone using a carboxylic acidfunctional compound having at least one group reactive with anisocyanate, such as a hydroxy carboxylic acid.

[0040] Alternatively, carbamate functional adducts made frompolyisocyanate functional compounds such as IPDI or TDI and hydroxycarbamate compounds can be made and then grafted onto acrylic, epoxy orother hydroxy functional polymers having acid numbers of at least 20,preferably 30. Of course, it will be appreciated that such resins musthave the characteristics required for in electrocoat compositions asdiscussed herein. Preferred polymers for use as the backbone of mostpreferred anodic compound (a) are hydroxyl functional acrylic resinswith acid numbers of at least 20, preferably at least 30.

[0041] A most preferred method of making most preferred anodic compound(a) suitable for use in the instant invention involves thecopolymerization of at least one carbamate functional monomer, at leastone unsaturated organic acid, at least one alkyl ester of an unsaturatedorganic acid and at least one additional ethylenically unsaturatedmonomer such as styrene. A most preferred reaction scheme involves thecopolymerization of CEMA, acrylic acid, styrene and butyl acrylate inthe presence of an azo or peroxide initiator.

[0042] The most preferred anodic compound (a) can be represented by therandomly repeating units according to the following formula:

[0043] In the above formula, R₁ represents H or CH₃. R2 represents H,alkyl, preferably of 1 to 6 carbon atoms, or cycloalkyl, preferably upto 6 ring carbon atoms. It is to be understood that the terms alkyl andcycloalkyl are to include substituted alkyl and cycloalkyl, such ashalogen-substituted alkyl or cycloalkyl. Substituents that will have anadverse impact on the properties of the cured material, however, are tobe avoided. For example, ether linkages are thought to be susceptible tohydrolysis, and should be avoided in locations that would place theether linkage in the crosslink matrix. The values x and y representweight percentages, with x being 10 to 90% and preferably 40 to 60%, andy being 90 to 10% and preferably 60 to 40%.

[0044] In the formula, A_(a) represents repeat units derived from one ormore ethylenically unsaturated monomers, at least one of which repeatunits must have a pendant carboxylic acid group. The at least onecarboxylic acid group may derive from the use of at least oneethylenically unsaturated monomer having at least one carboxylic acidgroup, preferably a pendant or terminal carboxylic acid group.Alternatively, the at least one repeating unit having a pendantcarboxylic acid may derive from the graft of a free organic acid to thepolymer backbone of the repeating units (A), as discussed above, whereinsuch free organic acid has a functional group reactive with the backbonepolymer.

[0045] Examples of ethylenically unsaturated monomers having a pendantcarboxylic acid group include acrylic acid, methacrylic acid, crotoicacid, vinylacetate acid, tiglic acid, 3,3-dimethylacrylic acid,trans-2-pentenoic acid, 4-pentenoic acid, trans-2-methyl-2-pentenoicacid, 6-heptanoic acid, 2-octenoic acid, and the like. Preferredethylenically unsaturated monomers having a pendant carboxylic acid areacrylic acid, methacrylic acid and mixtures there of.

[0046] Examples of free organic acids which may be used to graft apendant carboxylic acid group to the backbone polymer include compoundsof the formula HO—(R)—COOH or an amine salt of the formulaHO—(R)—COOH⁺NR₃, wherein R is an alkyl group of from 1 to 12 carbons,preferably from 2 to 8 carbons. Polyacids such as malic acid and citricacid may also be used. Preferred organic free acids are lactic acid,glycolic acid and stearic acid.

[0047] Other monomers which may be utilitzed to provide repeating units(A_(a)) of anodic compound (a) not having pendant carboxylic acidfunctionality are those monomers for copolymerization with acrylicmonomers known in the art and discussed above. These include alkylesters of acrylic or methacrylic acid, e.g., ethyl acrylate, butylacrylate, 2-ethylhexyl acrylate, butyl methacrylate, isodecylmethacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and thelike; and vinyl monomers such as unsaturated m-tetramethyl xyleneisocyanate (sold by American Cyanamid as TMI®), styrene, vinyl tolueneand the like.

[0048] L represents a divalent linking group, preferably an aliphatic of1 to 8 carbon atoms, cycloaliphatic, or aromatic linking group of 6 to10 carbon atoms. Examples of L include

[0049] —(CH₂)—, —(CH₂)₂—, —(CH₂)₄—, and the like. In one preferredembodiment, —L— is represented by —COO—L′— where L′ is a divalentlinking group. Thus, in a preferred embodiment of the invention, theanodic polymer compound (a) may be represented by randomly repeatingunits according to the following formula:

[0050] In this formula for most preferred anodic compound (a), R₁, R₂,A, x, and y are as defined above. L′ may be a divalent aliphatic linkinggroup, preferably of 1 to 8 carbon atoms, e.g., —(CH₂)—, —(CH₂)₂—,—(CH₂)₄—, and the like, or a divalent cycloaliphatic linking group,preferably up to 8 carbon atoms, e.g., cyclohexyl, and the like.However, other divalent linking groups can be used, depending on thetechnique used to prepare the polymer. For example, if a hydroxyalkylcarbamate is adducted onto an isocyanate-functional acrylic polymer, thelinking group L′ would include an —NHCOO— urethane linkage as a residueof the isocyanate group. Of course, A_(a) would still require thenecessary pendant carboxylic acid groups as discussed above.

[0051] Most preferred anodic compound (a) may be further characterizedby an acid number of from 20 to 80, preferably an acid number of from 30to 50 and most preferably an acid number of from 30 to 35.

[0052] Most preferred anodic compound (a) should also have a carbamateequivalent weight (grams of polymer (a)/equivalent of carbamate) of from150 to 1200, preferably from 200 to 600, and most preferably from 300 to400.

[0053] However, cationic compounds (a) are most preferred for use ascompound (a) in curable coating composition (I).

[0054] Examples of suitable cationic compounds (a) include resins whichare based on epoxy and bisphenol A and have one or more primary,secondary, tertiary, or quaternary ammonium groups. Illustrativeexamples of suitable cationic compounds (a) will generally have aminenumbers in the range of 0.1 to 1.0 meq. The weight average molecularweight (Mw) of such cationic compounds (a) will be from 300 to 100,000,preferably from 10,000 to 60,000.

[0055] Examples of suitable cationic compounds (a) include, withoutlimitation, polymers and resins such as acrylic, epoxy, polyurethane,alkyd, carbamate, polyesters, vinyl, epoxy, alkyds, mixtures thereof,and the like. Thus the one or more active hydrogen groups for suitablecathodic compounds (a) may generally be selected from the groupsconsisting of carboxylic acid, hydroxyl, carbamate, isocyanate, amine,epoxy, acrylate, vinyl, acetoacetate, mixtures thereof and the like,with hydroxyl, carbamate and mixtures thereof being preferred andhydroxyl, primary carbamate and mixtures thereof being most preferred.

[0056] Preferred cationic compounds (a) for use in curable coatingcomposition (I) are those containing at least one carbamate functionalgroup and one or more repeat units having at least one pendent cationicsalting site. Examples of suitable carbamate functional resins for usein cationic electrocoat compositions are described in pending U.S.patent application Ser. No. 09/217,917, entitled “Cathodic ElectrocoatHaving a Carbamate Functional Resin” all of which is hereby incorporatedby reference.

[0057] The most preferred cathodic compound (a) of the invention willhave at least one carbamate functional group appended to a polymerbackbone, preferably a plurality of pendant carbamate functional groups.It is preferred, but not necessary, that the polymer backbone to whichthe carbamate functional group is appended be an acrylic polymer.

[0058] The most preferred cathodic compound (a) can be prepared in avariety of ways.

[0059] One way to prepare such cathodic compounds (a) is to prepare anacrylic monomer having carbamate functionality in the ester portion ofthe monomer. Such monomers are well known in the art and are described,for example in U.S. Pat. Nos. 3,479,328, 3,674,838, 4,126,747,4,279,833, and 4,340,497, the disclosures of which are incorporatedherein by reference. One method of synthesis involves reaction of ahydroxy ester with urea to form the carbamyloxy carboxylate (i.e.,carbamate-modified acrylic). Another method of synthesis reacts anα,β-unsaturated acid ester with a hydroxy carbamate ester to form thecarbamyloxy carboxylate. Yet another technique involves formation of ahydroxyalkyl carbamate by reacting a primary or secondary amine ordiamine with a cyclic carbonate such as ethylene carbonate. The hydroxylgroup on the hydroxyalkyl carbamate is then esterified by reaction withacrylic or methacrylic acid to form the monomer. Other methods ofpreparing carbamate-modified acrylic monomers are described in the art,and can be utilized as well. The acrylic monomer can then be polymerizedalong with other ethylenically-unsaturated monomers, if desired, bytechniques well-known in the art. In a preferred embodiment, at leastone of the ethylenically unsaturated monomers will have a pendantcationic salting group.

[0060] As used herein, the term “cationic salting site” refers to afunctional group which is sufficiently basic to undergo reaction with anacid to produce a salt, which, while in an aqueous dispersion in thepresence of a voltage, will undergo decomposition and facilitate theformation of a insoluble polymer which deposits on a substrate immersedin the aqueous dispersion. Preferred cationic salting groups are aminefunctional groups and quaternary ammonium salts. The amine functionalgroups of the polymer (a) may be primary, secondary, tertiary aminogroups or quaternary ammonium salts. Quaternary ammonium salts andtertiary amines are most preferred, with quaternary ammonium saltsespecially preferred. Such groups may also be part of polyamines and/oralkanol amines.

[0061] The cationic salting site can be incorporated into or grafted tothe cathodic compound (a) polymer backbone in a variety of ways.

[0062] For example, a carbamate functional acrylic monomer can becopolymerized with an ethylenically unsaturated monomer having at leastone cationic salting group. The cationic salting group may be a primary,secondary, or tertiary amine functional group, or a quaternary ammoniumsalt, or a mixture thereof. Illustrative examples of such monomers aremethacrylamide, acrylamide, dimethylaminoethyl methyacrylate, mixturesthereof, and the like. Another example of a suitable ethylenicallyunsaturated monomer having amino functionality is the reaction productof glycidyl methacrylate and a tertiary amine salt. Dimethylaminoethylmethacrylate is preferred.

[0063] Alternatively, as will be discussed below, a polymer havingoxirane or glycidyl functionality can be made and the cationic saltinggroup formed by reaction of the glycidyl group with an amine or apolyamine. Amines or polyamines may be used having primary, secondary,or tertiary amine groups. Tertiary amine salts may be used to formquaternary ammonium salts via reaction with the glycidyl group on thepolymer backbone and are preferred.

[0064] Finally, a monomer such as glycidyl methacrylate can bepolymerized with a ethylenically unsaturated carbamate functionalmonomer to produce a carbamate functional acrylic having pendentglycidyl functionality. A cationic salting site can be incorporated byreaction of an amine functional compound, polyamine, or tertiary aminesalt with the oxirane group.

[0065] Preferred methods of preparing the cathodic compound (a) havingan acrylic backbone include the following.

[0066] One or more carbamate functional monomers such as 2-carbamateethyl methyacrylate (CEMA) may be copolymerized with at least oneethylenically unsaturated amine functional compound, at least one alkylester of an unsaturated organic acid and at least one otherethylenically unsaturated monomer such as styrene in the presence of asuitable initiator such as an azo or peroxide initiator. Other suitablecarbamate functional monomers include those discussed above.Illustrative suitable unsaturated amine functional compounds are asdiscussed above. A preferred unsaturated amine functional compound isdimethylaminoethyl methyacrylate. Examples of suitable alkyl esters ofunsaturated organic acid include ethyl acrylate, butyl acrylate,2-ethylhexyl acrylate, butyl methyacrylate, isodecyl methyacrylate,hydroxyethyl methacrylate, hydroxypropyl methacrylate, and the like.Preferred alkyl esters are nonhydroxy functional monomers such as butylacrylate and butylmethacrylate. A preferred monomer for use as anadditional ethylenically unsaturated monomer is styrene.

[0067] In another reaction scheme, an adduct may be made from apolyisocyanate such as isophorone diisocyanate (IPDI) or toluenediisocyanate (TDI) and a hydroxy functional carbamate compound such ashydroxypropyl carbamate. The resulting adduct can then be grafted ontoan acrylic, epoxy or other hydroxy functional resin having suitablecharacteristics for use.

[0068] Another method involves a multistep reaction wherein a hydroxycarbonate may reacted with ammonia or an amine functional compound toprovide a primary, secondary or tertiary carbamate functional compound.This compound is then reacted with an anhydride compound via thereaction of the hydroxy group with the anhydride ring. The carboxylicacid groups of the resulting reaction product are then reacted with theoxirane groups of a glycidyl ether of Bisphenol A. Cationic saltinggroups are incorporated via the reaction of an amine functionalcompound, such as diethanol amine, with the glycidyl ether groups whichterminate the resulting hydroxy and carbamate functional polymer.

[0069] In an alternative reaction, an isocyanate functional monomer suchas unsaturated m-tetramethyl xylene isocyanate (sold by AmericanCyanamid as TMI®) can be copolymerized with monomers such as alkylesters such as described immediately above such as butyl acrylate andunsaturated monomers such as styrene to produce an isocyanate functionalpolymer. The required cationic salting group functionality and carbamatefunctionality can then be grafted onto the isocyanate functional polymerby a multi-stage reaction having a first stage using a carbamatefunctional monomer such as hydroxypropyl carbamate followed by a secondstage using an amine functional compound, i.e., primary, secondary ortertiary amine groups, most preferably an alkanol amine.

[0070] In general, the most preferred cathodic compound (a) can berepresented by the randomly repeating units according to the followingformula:

[0071] In the above formula, R₁ represents H or CH₃. R₂ represents H,alkyl, preferably of 1 to 6 carbon atoms, or cycloalkyl, preferably upto 6 ring carbon atoms. It is to be understood that the terms alkyl andcycloalkyl are to include substituted alkyl and cycloalkyl, such ashalogen-substituted alkyl or cycloalkyl. Substituents that will have anadverse impact on the properties of the cured material, however, are tobe avoided. For example, ether linkages are thought to be susceptible tohydrolysis, and should be avoided in locations that would place theether linkage in the crosslink matrix. The values x and y representweight percentages, with x being 10 to 90% and preferably 40 to 60%, andy being 90 to 10% and preferably 60 to 40%.

[0072] In the formula, A_(c) represents comprises one or more repeatunit having a pendent cationic salting site. Such repeat units may bederived from one or more ethylenically unsaturated monomers, at leastone of which repeat units must have a pendent cationic salting group,preferably an amino group. As discussed above, the at least one cationicsalting group may derive from the use of at least one ethylenicallyunsaturated monomer having at least one amino group. Alternatively, theat least one repeating unit having a pendent cationic salting site mayderive from the reaction of an amine functional compound with a glycidylgroup previously incorporated into the polymer.

[0073] L represents a divalent linking group and is the same asdiscussed above with respect to the anodic compound (a).

[0074] In an especially preferred embodiment of cathodic compound (a),cathodic compound (a) will comprise a polymer (A) which may be made viathe grafting of a carbamate functional intermediate adduct (A′) onto anacrylic, epoxy, or other hydroxy functional resin (A″) having suitablecharacteristics for use as discussed below. In a most preferred reactionscheme, a carbamate functional intermediate adduct (A′) may be made fromthe reaction of a polyisocyanate (ai) and a carbamate functionalcompound (aii) comprising at least one group which is reactive withisocyanate. Preferably, the compound (aii) will comprise at least oneprimary carbamate group.

[0075] Suitable polyisocyanates (ai) are monomeric polyisocyanates thatcan be aliphatic, cycloaliphatic, and/or aromatic polyisocyanates.Useful aliphatic polyisocyanates include aliphatic diisocyanates such asethylene diisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane,1,6-diisocyanatohexane, 1,4-butylene diisocyanate, lysine diisocyanate,1,4-methylene bis-(cyclohexyl isocyanate) and isophorone;pxdiisocyanate. Useful aromatic diisocyanates and araliphaticdiisocyanates include the various isomers of toluene diisocyanate,meta-xylylenediioscyanate and para-xylylenediisocyanate, also4-chloro-1,3-phenylene diisocyanate, 1,5-tetrahydro-naphthalenediisocyanate, 4,4′-dibenzyl diisocyanate and 1,2,4-benzene triisocyanatecan be used. In addition, the various isomers of α,α,α′,α′-tetramethylxylene diisocyanate can be used. Biurets of isocyanates such asDESMODUR® NlOO from Bayer may also be useful. Preferably, polyisocyanate(ai) is a diisocyanate. Isophorone diisocyanate is most preferred.

[0076] Suitable examples of such isocyanate reactive, carbamatefunctional compounds are commercially available hydroxy functionalcarbamate compounds such as hydroxypropyl carbamate, hydroxybutylcarbamate, and mixtures thereof. Hydroxypropyl carbamate is mostpreferred. It is also within the scope of the invention to useisocyanate reactive compounds containing groups convertible to carbamatein place of the isocyanate reactive, carbamate functional compounds. Useof the term “convertible to carbamate” refers to groups which have thecapability of forming carbamate groups, preferably primary carbamategroups after reaction with the polyisocyanate is completed. Examples ofgroups convertible to carbamate include cyclic carbonate groups, (i.e.,the reaction product of glycidol and CO₂ then reacted with ammonia toform a carbamate group), and epoxy groups (i.e., reaction of the epoxywith CO₂ to form cyclic carbonate followed by reaction with ammonia).

[0077] The isocyanate reactive, carbamate functional compound (aii) isreacted with the polyisocyanate (ai) to provide an intermediate compound(A′) having at least one carbamate group, preferably at least oneprimary carbamate group, and at least one isocyanate group.

[0078] In a particularly preferred embodiment, the isocyanate reactivecarbamate functional compound (aii) will be reacted with thepolyisocyanate (ai) under reaction conditions sufficient to produce boththe intermediate (A′) having both carbamate functionality and isocyanatefunctionality as well as a carbamate functional reactive additive (B)which is free of isocyanate functionality. In this embodiment, both (B)and (A′) are the reaction products of a single reaction. Accordingly,(B) may be described as being generated “in situ” during the productionof intermediate (A′). Examples of suitable reaction conditions include amole equivalent ratio of NCO to hydroxyl of from 2/1 to 2/2, preferablyfrom 1.2 to 1.8, and most preferably from 1.3 to 1.7. Other reactionconditions to consider include temperature and catalyst type and level.However, it will be appreciated that in situ reactive additive (B) is anoptional element with respect to the instant invention.

[0079] Suitable catalysts which may be used for the multistep productionof the polymer (A) include those described below with respect to thecurable coating compositions (I) and (II). Preferred catalysts are thosesuch as Lewis acids or tin salts. A most preferred catalyst is dibutyltin dilaurate. Preferably, the catalyst will be used in an amount offrom 0.001 to 1%, and most preferably from 0.05 to 0.15%, based onsolids.

[0080] In situ generated reactive additive (B) will have a numberaverage molecular weight of from 250 to 2000 and most preferably from400 to 800. Preferably, reactive additive (B) will have a degree ofcarbamate functionality equal to the degree of isocyanate functionalityof polyisocyanate (ai), i.e., the polyisocyanate (ai) will preferably bediblocked for the reactive additive (B) when polyisocyanate (ai) is adiisocyanate.

[0081] The carbamate functional/isocyanate functional intermediate (A′)is then grafted onto an acrylic, epoxy or other hydroxy functional resin(A″) having suitable characteristics for use to form the most preferredembodiment of cathodic compound (a). The grafting of the intermediate(A′) must occur via reaction with the at least one isocyanate group of(A′) with a reactive group of (A″).

[0082] Most preferably, the carbamate functional/isocyanate functionalintermediate (A′) will be grafted onto a hydroxy functional compound(A″) comprising epoxy groups. The grafting of (A′) will thus occur viareaction between a hydroxyl group and the at least one isocyanate groupof (A′). Preferably, the hydroxy functional compound comprising epoxygroups will be an epoxy functional resin. As discussed below, reactionof the epoxy group with a tertiary amine in the presence of an acid is apreferred method of incorporating the most preferred one or morequaternary ammonium groups.

[0083] Suitable epoxy containing polymers are resinous polyepoxide orpolymeric resinous materials containing two or more 1,2-epoxy groups permolecule. Preferred polyepoxides are polyglycidyl ethers of polyhydricphenols such as bisphenol A. These can be produced by etherification ofa polyphenol with an epihalohydrin or dihalohydrin such asepichlorohydrin or dichlorohydrin in the presence of alkali. Suitablepolyhydric phenols include bis-2,2-(4-hydroxyphenyl)propane,bis-1,1-(4-hydroxyphenyl)ethane, bis(2-hydroxynaphthyl)methane and thelike.

[0084] Other useful polyepoxide compounds are those made from novolakresins or similar polyhydroxyphenol resins.

[0085] Also suitable are polyglycidyl ethers of polyhydric alcohols suchas ethylene glycol, propylene glycol, diethylene glycol and triethyleneglycol.

[0086] There can also be used polyglycidyl esters of polycarboxylicacids which are produced by the reaction of epichlorohydrin or a similarepoxy compound with an aliphatic or aromatic polycarboxylic acid such assuccinic acid and terepthalic acid.

[0087] Most preferably, the epoxy-containing compound to which thecarbamate functional intermediate is grafted onto will be the reactionproduct of a liquid epoxy such as diglycidyl ether of bisophenol A(DGEBA) and bisphenol A. Particularly preferred examples of such epoxycontaining compounds may be characterized as upgraded epoxy resinshaving epoxy equivalent weights of approximately 1100. Suitable liquidepoxys are GY2600, commercially available from Ciba Geigy and Epon® 828,commercially available from Shell Chemical Company.

[0088] Thus, a most preferred cathodic compound (a) will comprise bothpolymer (A) and optional carbamate functional reactive additive (B)generated during the production of polymer (A), most specifically duringthe production of intermediate (A′). Reactive additive (B) will bepresent in the resin composition of the invention in an amount of from 1to 20, preferably from 2 to 15 and most preferably from 3 to 10 percent,based on the total resin solids. The cathodic compound (a) comprisingboth polymer (A) and polycarbamate functional reactive additive (B) thatis free of isocyanate functionality has been found to provide unexpectedbenefits in both application and performance.

[0089] In this most preferred embodiment of cathodic compound (a),polymer (A) comprises one or more quaternary ammonium groups which serveas cationic salting sites. While it most preferred that polymer (A)comprise one or more quaternary ammonium groups, other cationic saltinggroups may also be present in polymer (A). Examples of other suitablecationic salting groups are amine functional groups such as primary,secondary, tertiary amino groups or mixtures thereof.

[0090] Polymer (A) may be further characterized by a meq of cationicsalting group, preferably a quaternary ammonium group, of from about 0.1to 2.0 meq N/gram polymer (A), preferably from about 0.2 to 1.5 meqN/gram polymer (A), and most preferably from about 0.3 to 0.6 meq N/grampolymer (A). It is preferred that at least 80% of the total number ofcationic salting groups be quaternary ammonium groups, more preferablyfrom 90 to 100% of the total number of cationic salting groups, and mostpreferably from 95 to 100% of the total number. The remaining cationicsalting groups can be as described above, with secondary amino groupsbeing most preferred.

[0091] A preferred method of incorporating the necessary cationicsalting group, i.e., a quaternary ammonium group into the polymer (A),is by reaction of a glycidyl group with one or acid salts of one or moretertiary amines. The acid salt will preferably be preformed via themixing of one or more tertiary amines and one or more acids. Otheramines or polyamines may be used having primary, secondary, tertiaryamine groups, or mixtures thereof. However, it will be appreciated thatquaternary ammonium groups are an especially preferred element ofpolymer (A) of cathodic compound (a). Suitable acids are carboxylicacids such as lactic acid and acetic acid.

[0092] Epoxy functionality will most preferably be present in polymer(A) as a result of the foregoing reaction scheme wherein anisocyanate/carbamate functional intermediate (A′) is grafted onto ahydroxy/epoxy functional compound.

[0093] Alternatively, epoxy functionality can be incorporated into anacrylic resin via the polymerization of a monomer such as glycidylmethacrylate with an ethylenically unsaturated carbamate functionalmonomer to produce a carbamate functional acrylic having pendentglycidyl functionality. Subsequently, a cationic salting site, i.e., aquaternary ammonium compound can be incorporated by reaction of atertiary amine with the oxirane group in the presence of an acid.

[0094] In the absence of an epoxy group, the cationic salting site canbe incorporated into or grafted to the polymer (A) backbone in a varietyof ways.

[0095] For example, a carbamate functional acrylic monomer can becopolymerized with an ethylenically unsaturated monomer having at leastone cationic salting group. One or more carbamate functional monomerssuch as 2-carbamate ethyl methyacrylate (CEMA) may be copolymerized withat least one ethylenically unsaturated amine functional compound, atleast one alkyl ester of an unsaturated organic acid and at least oneother ethylenically unsaturated monomer such as styrene in the presenceof a suitable initiator such as an azo or peroxide initiator. Othersuitable carbamate functional monomers include those discussed above.

[0096] The cationic salting group of the ethylenically unsaturatedmonomer may be a primary, secondary, or tertiary amine functional group,or a quaternary ammonium salt, or a mixture thereof. Most preferably,the salting group will be a quaternary ammonium salt. Illustrativesuitable unsaturated amine functional compounds are methacrylamide,acrylamide, dimethylaminoethyl methyacrylate, mixtures thereof, and thelike. A preferred unsaturated amine functional compound isdimethylaminoethyl methyacrylate.

[0097] Examples of suitable alkyl esters of unsaturated organic acidinclude ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, butylmethyacrylate, isodecyl methyacrylate, hydroxyethyl methacrylate,hydroxypropyl methacrylate, and the like. Preferred alkyl esters arenonhydroxy functional monomers such as butyl acrylate andbutylmethacrylate. A preferred monomer for use as an additionalethylenically unsaturated monomer is styrene.

[0098] A preferred example of a suitable ethylenically unsaturatedmonomer having amino functionality is the reaction product of glycidylmethacrylate and the acid salt of a tertiary amine. Dimethylaminoethylmethacrylate is most preferred as the tertiary amine.

[0099] If curable coating composition (I) is a cationic electrocoatcomposition, the cationic compound (a) will be preferably reacted withan acid for use in the cathodic electrocoat coating composition of theinvention. This reaction may be termed “neutalization or “acid-salted”and specifically refers to the reaction of the pendent amino groups withan acidic compound in an amount sufficient to neutralize enough of thebasic amino groups to impart water-dispersibility to compound (a).Illustrative acid compounds include phosphoric acid, propionic acid,acetic acid, lactic acid, or citric acid.

[0100] Curable coating composition (I) will further comprise a curingagent (b). Curing agent (b) is a compound having a plurality offunctional groups that are reactive with the active hydrogen-containinggroups on compound (a). Such reactive groups include active methylol ormethylalkoxy groups, isocyanate groups, siloxane groups, cycliccarbonate groups, and anhydride groups. Examples of compounds suitablefor use as curing agent (b) include aminoplast resins,phenol/formaldehyde adducts, blocked isocyanate curing agents,tris(alkoxy carbonylamino) triazines (available from Cytec Industriesunder the tradename TACT) and mixtures thereof. Aminoplast resins andphenol/formaldehyde adducts are most preferred, with blocked isocyanatesbeing disfavored. Suitable aminoplast resins are amine/aldehydecondensates, preferably at least partially etherified, and mostpreferably fully etherified. Melamine and urea are preferred amines, butother triazines, triazoles, diazines, guanidines, or guanamines may alsobe used to prepare the alkylated amine/aldehyde aminoplast resinscrosslinking agents. The aminoplast resins are preferablyamine/formaldehyde condensates, although other aldehydes, such asacetaldehyde, crotonaldehyde, and benzaldehyde, may be used.Non-limiting examples of preferred aminoplast resins include monomericor polymeric melamine formaldehyde resins, including melamine resinsthat are partially or fully alkylated using alcohols that preferablyhave one to six, more preferably one to four, carbon atoms, such ashexamethoxy methylated melamine; urea-formaldehyde resins includingmethylol ureas and siloxy ureas such as butylated urea formaldehyderesin, alkylated benzoguanimines, guanyl ureas, guanidines,biguanidines, polyguanidines, and the like. Monomeric melamineformaldehyde resins are particularly preferred. The preferred alkylatedmelamine formaldehyde resins are water miscible or water soluble.

[0101] Suitable ionic compounds (a) and curing agent (b) intended foruse in curable coating composition (I) will be dispersed in aqueousmedium. The term “dispersion” as used within the context of the presentinvention is believed to be a two-phase translucent or opaque aqueousresinous system in which the resin is in the dispersed phase and waterthe continuous phase. It will be appreciated that in this case, curingagent (b) may or may not be soluble in water. The average particle sizediameter of the resinous phase is about 0.05 to 5.0 microns, preferablyless than 2.0 microns.

[0102] The concentration of the ionic compound (a) and curing agent (b)in the aqueous medium is, in general, not critical, but ordinarily themajor portion of the aqueous dispersion is water. The aqueous dispersionof coating composition (I) will usually contain from about 3 to 50percent, preferably 10 to 40 percent by weight resin solids. Aqueousresin concentrates which are to be further diluted with water, generallyrange from 10 to 30 percent by total weight solids.

[0103] The curable coating composition (I) may, and most preferably willcontain one or more catalyst (c) to facilitate the reaction betweencompound (a) and curing agent (b). For example, a strong acid catalystmay be utilized to enhance the cure reaction. It will be appreciatedthat such catalysts may be blocked or unblocked. Such catalysts arewell-known in the art and include, for example, p-toluenesulfonic acid,dinonylnaphthalene disulfonic acid, dodecylbenzenesulfonic acid (DDBSA),phenyl acid phosphate, monobutyl maleate, butyl phosphate, and hydroxyphosphate ester. Other catalysts useful in the composition of theinvention include Lewis acids, zinc salts, and tin salts. IllustrativeLewis acids or zinc salts are zinc nitrate, zinc acetate, bismuthoctoate, dibutyltin dilaurate, and the like. Such catalysts willtypically be used in an amount of from 0.1 to 3.0 weight percent, basedon the resin solids, preferably from 0.5 to 2.0 weight percent, based onthe resin solids. Preferred catalysts for use in curable coatingcomposition (I) are Lewis acids such as zinc nitrate and blocked andunblocked acid catalysts such as DDBSA. It is also within the scope ofthe instant invention that curable coating composition (I) be catalyztedby acid available from curable coating composition (II) such asdiscussed below.

[0104] In an especially preferred embodiment, curable coatingcomposition (I) will further comprise an optional reactive additive (C)such as is described in U.S. patent application entitled “CathodicElectrocoat Having A Carbamate Functional Resin And A CarbamateFunctional Reactive Additive”, filed on the same day as the instantapplication.

[0105] Compounds suitable for use as reactive additive (C) are thosehaving at least one primary carbamate group and at least one alkylradical selected from the group consisting of straight chain alkylgroups of more than 10 carbons, branched alkyl groups of from 5 to 30carbons, and mixtures thereof.

[0106] As used herein, “primary carbamate group” refers to thefunctional group having the structure

[0107] Thus, the primary carbamate group of the invention may be definedas a terminal or pendent carbamate group. Although compounds suitablefor use as reactive additive (C) may comprise more than one primarycarbamate group, it is most preferred that such compounds have oneprimary carbamate group.

[0108] In addition to the at least one primary carbamate group,compounds suitable for use as reactive additive (C) will furthercomprise at least one alkyl group selected from the group consisting ofbranched alkyl groups having from 5 to 30 total carbons, straight chainalkyl groups of more than 10 carbons, and mixtures thereof.

[0109] As used herein, the term “branched” refers to both lateralbranches and forked branches. Lateral refers to a branch of two smallchains at the end atom of a carbon chain. Forked refers to a branch oftwo small chains in the middle of a carbon chain. For the purposes ofthe instant invention a carbon chain may be from 1 to 15 carbons, morepreferably from 1 to 8 and most preferably from 1 to 3. The total numberof carbon atoms in the branched alkyl group is obtained by adding thetotal number of carbons in the main carbon chain+the number of carbonsin all alkyl chains extending from the main carbon chain.

[0110] It will be appreciated that the main carbon chain may be from 1to 25 carbons, preferably from 1 to 10, most preferably from 1 to 4.Most preferably, the main chain will be an aliphatic carbon chain freeof unsaturation. Although the at least one branched alkyl group maycomprise from 5 to 30 total carbons, more preferably, it will have from5 to 15 carbons and most preferably from 8 to 12 carbons.

[0111] Finally, it will be appreciated that suitable “at least one alkylgroups” for use in reactive additive (C) will be substantially free offunctional groups that are reactive with one or more of components (A)and (B). Thus, the at least one alkyl group selected from the groupconsisting of branched alkyl groups having from 5 to 30 total carbons,straight chain alkyl groups of more than 10 carbons, and mixturesthereof, will be free of hydroxyl groups and the like.

[0112] An example of an especially suitable at least one branched alkylgroup is

[0113] wherein R₁, R₂, and R₃ are alkyl groups of from 1 to 10 carbonseach, preferably aliphatic groups of from 1 to 10 carbons. Mostpreferably, R₁, R₂, and R₃ will total from 8 to 12 carbons with at leastone of R₁, R₂, and R₃ being a methyl group.

[0114] In another suitable branched alkyl group of the same structure,one of R₁, R₂, and R₃, maybe hydrogen, with the other substituent groupsbeing alkyl groups of from 1-10 carbons, preferably aliphatic groups offrom 1 to 10. An example of such a group is

[0115] In this instance, the above structure is understood to be anexample of lateral branching.

[0116] In a particularly preferred embodiment, the at least one branchedalkyl group will comprise

[0117] wherein x+y=5 carbons.

[0118] Alternatively, the compound suitable for use as reactive additive(C) may include a straight chain alkyl group of more than 10 carbons,preferably more than 15 carbons and most preferably more than 18.Examples of suitable straight chain, aliphatic alkyl groups include1-eicosanyl, 1-octadecyl, 1-arachidyl, 1-dodecyl, 1-decyl, and 1-octyl,and the like. It is most preferred that compounds suitable for use asreactive additive (C) include at least one group which is a branchedalkyl group such as described above.

[0119] Compounds suitable for use as reactive additive (C) may furtherinclude heteratoms such as O and N, most preferably O. Such heteratomsmay be incorporated in the form of groups such as esters, hydroxyls,ether, carboxyls, mixtures thereof and the like. Preferred are esters,hydroxyls, and mixtures thereof. Most preferably, a compound willcomprise at least one hydroxyl group and one ester group in addition tothe carbamate functional group and the at least one alkyl group. Asindicated above, such heteratoms may not be present in the branchedalkyl group nor in the straight alkyl chain group of more than 10carbons.

[0120] Particularly suitable compounds for use as reactive additive (C)are those having the formula:

[0121] wherein X is a branched alkyl radical of from 5 to 30 totalcarbons, more preferably from 5 to 15 total carbons and most preferablyfrom 8 to 12 total carbons.

[0122] A more preferred compound for use as reactive additive (C) isthat having the formula:

[0123] wherein R₁, R₂, and R₃ are each alkyl groups of from 1 to 10carbons, especially compounds wherein R₁, R₂, and R₃ total from 8 to 12carbons with at least one of R₁, R₂, and R₃ being a methyl group.

[0124] The most preferred compound for use as reactive additive (C) isthat having the formula:

[0125] wherein R₂ and R₃ are respectively —(CH₂)_(x)CH₃ and—(CH₂)_(y)CH₃ wherein x+y=5.

[0126] Besides water, the aqueous medium of curable coating composition(I) may also contain a coalescing solvent. Useful coalescing solventsinclude hydrocarbons, alcohols, esters, ethers and ketones. Thepreferred coalescing solvents include alcohols, polyols and ketones.Specific coalescing solvents include monobutyl and monohexyl ethers ofethylene glycol, and phenyl ether of propylene, ethylene glycol butylether, ethyleneglycol dimethyl ether, or mixtures thereof. A smallamount of a water-immiscible organic solvent such as xylene, toluene,methyl isobutyl ketone or 2-ethylhexanol may be added to the mixture ofwater and the water-miscible organic solvent. The amount of coalescingsolvent is not unduly critical and is generally between about 0 to 15percent by weight, preferably about 0.5 to 5 percent by weight based ontotal weight of the resin solids.

[0127] The curable coating composition (I) may further containconventional pigments such as titanium dioxide, ferric oxide, carbonblack, aluminum silicate, precipitated barium sulfate, aluminumphosphomolybdate, strontium chromate, basic lead silicate or leadchromate. The pigment-to-resin weight ratio can be important and shouldbe preferably less than 50:100, more preferably less than 40:100, andusually about 10 to 30:100. Higher pigment-to-resin solids weight ratioshave also been found to adversely affect coalescence, flow, and/orcoating performance.

[0128] Curable coating composition (I) can contain optional ingredientssuch as wetting agents, surfactants, defoamers, antioxidants, UVabsorbers, light stabilizers, and so forth. Examples of surfactants andwetting agents include alkyl imidazolines such as those available fromCiba-Geigy Industrial Chemicals as Amine C®, acetylenic alcoholsavailable from Air Products and Chemicals as Surfynol® 104. Theseoptional ingredients, when present, constitute from about 0 to 20percent by weight of resin solids, and preferably from 0.1 to 1.0percent by weight of resin solids. Plasticizers are optional ingredientsbecause they promote flow. Examples are high boiling water immisciblematerials such as polyalkylene polyols, such as polypropylene polyols orethylene or propylene oxide adducts of nonyl phenols or bisphenol A.Plasticizers can be used and if so are usually used at levels of about 0to 15 percent by weight resin solids.

[0129] In general, sufficient water is added so that the dispersion ofcurable coating composition (I) has a solids content of more than 20,preferably more than 30% by weight.

[0130] The curable coating composition (I) should have anelectroconductivity from 0.1 to 5 mS/cm, preferably from 0.5 to 3 mS/cm.When this value is too low, it is difficult to obtain a film thicknesshaving desired protective and other functions. Conversely, if thecomposition is too conductive, problems such as the dissolution ofsubstrate or counter electrode in the bath, uneven film thickness orpoor water or corrosion resistance may arise.

[0131] The curable coating composition (I) will be applied on aconductive substrate by the electrodeposition coating process at anonvolatile content of 10 to 25% by weight to a dry film thickness of 15to 35 microns. Electrodeposition of the coating preparations accordingto the invention may be carried out by any of a number of processesknown to those skilled in the art. The deposition may be carried out onall electrically conducting substrates, for example metal, such assteel, copper, aluminum and the like.

[0132] The curable coating composition (I) will not be immediately curedas in traditional prior art electrocoat processes. Rather, the curablecoating composition will be maintained in a substantially uncured state.As used herein, the term “uncured” refers to a coating which has notbeen subjected to conditions sufficient to initiate crosslinking of thecompound (a) and curing agent (b). However, it is within the scope ofthe instant claimed method that curable coating composition (I) beexposed to conditions sufficient to effect removal of water from curablecoating composition (I). It is preferred that applied curable coatingcomposition (I) be subjected to a ‘water removal flash’ of either an IRsource or to a condition of elevated heat. Conditions of elevated heatare most preferred. If an IR source is used, the IR source should becapable of providing from ______ to ______ (energy units/unit of time?),and most preferably from ______ to ______. Alternatively, if traditionalelevated heat is employed, the applied curable coating composition maybe subjected to temperatures of from 60 to 120° C. for a period of from1 to 10 minutes, most preferably from 90 to 110° C. for a period of from1 to 3 minutes. Sources of elevated heat are traditional baking ovensand blackwall radiation. Traditional baking ovens such as are well knownin the art are most preferred.

[0133] The curable coating composition (II) may then be applied to theapplied but uncured curable coating composition (I). Application ofcurable coating composition may be done via known application methodssuch as spraying, electrophoretic deposition, powder slurry sprayapplication, powder coating via fluidized bed or the like. However,spray application of curable coating composition (II) is most preferred.

[0134] Curable coating composition (II) may a primer, sealer, basecoat,topcoat, or a mixture thereof. Most preferably, composition (II) will bea primer or sealer composition. Aqueous compositions or those having lowconcentrations of volatile organic compounds (VOC) such as powdercoatings and powder slurry coatings are preferred. In a most preferredembodiment, curable coating composition (II) will be an aqueous powderslurry composition.

[0135] Curable coating composition (II) will comprise a compound (a)comprising one or more active hydrogen-containing groups and a curingagent (b) comprising one or more groups reactive with activehydrogen-containing groups. It will be appreciated that the compositionof curable coating composition (II) is not restricted so long as therequirement with respect to curing agents (I) and (II) is met, i.e.,that curing agents (I) and (II) be essentially interchangeable asdiscussed above and below.

[0136] Examples of suitable compounds (a) for use in curable coatingcomposition (II) include all well known polymers and/or resins such asacrylics, polyesters, epoxys, polyurethanes, vinyl, polycarbonates,alkyds, polysiloxanes, and mixtures and copolymers thereof. Acrylic,polyurethane, and polyester resins and mixtures thereof, are preferred,with acrylic, polyurethane and mixtures thereof being most preferred.The one or more active hydrogen sites may thus be selected from thegroup consisting of hydroxyl, carboxylic acid, epoxy, carbamate,isocyanate, amine, acrylate, vinyl, silane, acetoacetate, mixturesthereof, and the like. Hydroxyl groups are most preferred.

[0137] A most preferred compound (a) for curable coating composition(II) will comprise a combination of a polyurethane polymer and anacrylic polymer. The polyurethane polymer will most preferably have aglass transition temperature of 0° C. or less. The acrylic polymer willmost preferably have a glass transition temperature that is at leastabout 20° C. higher than the glass transition temperature ofpolyurethane resin.

[0138] The polyurethane polymer preferred for use as compound (II)(a)has a glass transition temperature of about 0° C. or less, preferablyabout −20° C. or less, and more preferably about −30° C. or less. Theglass transition temperature of the polyurethane is in the range of fromabout −80° C. to about 0° C., more preferably from about −65° C. toabout −10° C., still more preferably from about −65° C. to about −30°C., and even still more preferably from about −60° C. to about −35° C.

[0139] The weight average molecular weight of the polyurethane preferredfor use as compound (II)(a) is preferably from about 15,000 to about60,000, more preferably from about 15,000 to about 60,000, and even morepreferably from about 20,000 to about 35,000.

[0140] Polyurethanes are prepared by reaction of at least onepolyisocyanate and at least one polyol. The reactants used to preparethe polyurethane are selected and apportioned to provide the desiredglass transition temperature. Suitable polyisocyanates include, withoutlimitation, aliphatic linear and cyclic polyisocyanates, preferablyhaving up to 18 carbon atoms, and substituted and unsubstituted aromaticpolyisocyanates. Illustrative examples include, without limitation,ethylene diisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane,1,4-butylene diisocyanate, lysine diisocyanate, 1,4-methylenebis(cyclohexyl isocyanate), isophorone diisocyanate, toluenediisocyanates (e.g., 2,4-toluene diisocyanate and 2,6-toluenediisocyanate) diphenylmethane 4,4′-diisocyanate,methylenebis-4,4′-isocyanatocyclohexane, 1,6-hexamethylene diisocyanate,p-phenylene diisocyanate, tetramethyl xylene diisocyanate, meta-xylenediisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate,1,12-dodecamethylene diisocyanate, cyclohexane-1,3- and-1,4-diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane, andcombinations of two or more of these. Biurets, allophonates,isocyanurates, carbodiimides, and other such modifications of theseisocyanates can also be used as the polyisocyanates. In a preferredembodiment, the polyisocyanates includemethylenebis-4,4′-isocyanatocyclohexane, 1,6-hexamethylene diisocyanate,1,12-dodecamethylene diisocyanate, and combinations thereof. It isparticularly preferred to use at least one α,ω)-alkylene diisocyanatehaving four or more carbons, preferably 6 or more carbons, in thealkylene group. Combinations of two or more polyisocyanates in which oneof the polyisocyanates is 1,6-hexamethylene diisocyanate are especiallypreferred.

[0141] The polyol or polyols used to prepare the polyurethane polymercan be selected from any of the polyols known to be useful in preparingpolyurethanes, including, without limitation, 1,4-butanediol,1,3-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol,1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol,ethylene glycol, diethylene glycol, triethylene glycol and tetraethyleneglycol, propylene glycol, dipropylene glycol, glycerol,cyclohexanedimethanols, 2-methyl-2-ethyl-1,3-propanediol,2-ethyl-1,3-hexanediol, thiodiglycol, 2,2,4-trimethyl-1,3-pentanediol,cyclohexanediols, trimethylolpropane, trimethylolethane, and glycerin;polyester polyols such as the reaction products of any of the foregoingalcohols and combinations thereof with one or more polycarboxylic acidsselected from malonic acid, maleic acid, succinic acid, glutaric acidadipic acid, azelaic acid, anhydrides thereof, and combinations thereof;polyether polyols, such as polyethylene glycols and polypropyleneglycols; and combinations of such polyols. Polyols having two hydroxylgroups are preferred. The polyurethane is preferably prepared using oneor more polyester polyols. In a preferred embodiment, the polyesterpolyol is the reaction product of a mixture that comprises neopentylglycol and adipic acid.

[0142] While it is possible to prepare a nonionic dispersion of thepolyurethane, the polyurethane dispersion used as part of most preferredcompound (II)(a) is preferably anionic. Acid-functional polyurethanesthat can be salted to form anionic dispersions or emulsions may besynthesized by including a monomer having acid functionality, such as,without limitation, dialkylpropionic acids including dimethylolpropionicacid, and alkali metal salts of amino acids such as taurine, methyltaurine, 6-amino caproic acid, glycine, sulfanilic acid, diamino benzoicacid, ornithine, lysine and 1:1 adducts of sultones, such as propanesultone or butane sultone, with diamines, such as ethylene diamine,hydrazine, or 1,6-hexamethylene diamine. The hydroxyl groups react toform the urethane linkages while the acid group remains unreacted in thepolyurethane polymerization.

[0143] Suitable polyurethane polymers can be prepared by any of theknown methods. In one method for preparing polyurethane polymers, thepolyisocyanate component is reacted with an excess of equivalents of thepolyol component to form a hydroxyl-functional polyurethane polymer.Alternatively, an excess of equivalents of the polyisocyanate componentcan be reacted with the polyol component to form anisocyanate-functional prepolymer. The prepolymer can then be reactedfurther in different ways. First, the prepolymer can be reacted with amono-functional alcohol or amine to provide a non-functionalpolyurethane polymer. Examples of mono-functional alcohols and aminesthat may be used include polyethylene oxide compounds having oneterminal hydroxyl group, lower mono-functional alcohols having up to 12carbon atoms, amino alcohols such as dimethylethanolamine, and secondaryamines such as diethylamine and dimethylamine. Secondly, the prepolymercan be reacted with a polyfunctional polyol, polyamine, or amino alcoholcompound to provide reactive hydrogen functionality. Examples of suchpolyfunctional compounds include, without limitation, the polyolsalready mentioned above, including triols such as trimethylolpropane;polyamines such as ethylenediamine, butylamine, and propylamine; andamino alcohols, such as diethanolamine. Finally, the prepolymer can bechain extended by the water during emulsification or dispersion of theprepolymer in the aqueous medium. The prepolymer is mixed with the waterafter or during neutralization.

[0144] The polyurethane preferred as part of compound (II)(a) may bepolymerized without solvent. Solvent may be included, however, ifnecessary, when the polyurethane or prepolymer product is of a highviscosity. If solvent is used, the solvent may be removed, partially orcompletely, by distillation, preferably after the polyurethane isdispersed in the water. The polyurethane may have nonionic hydrophilicgroups, such as polyethylene oxide groups, that serve to stabilize thedispersed polyurethane polymer. In a preferred embodiment, however, thepolyurethane polymer is prepared with pendant acid groups as describedabove, and the acid groups are partially or fully salted with an alkali,such as sodium or potassium, or with a base, such as an amine, before orduring dispersion of the polyurethane polymer or prepolymer in water.

[0145] In the most preferred embodiment, compound (II)(a) will alsoinclude an acrylic polymer. The acrylic polymer is prepared according tousual methods, such as by bulk or solution polymerization followed bydispersion in an aqueous medium or, preferably, by emulsionpolymerization in an aqueous medium. The acrylic polymer is polymerizedfrom a monomer mixture that preferably includes an activehydrogen-functional monomer and preferably includes an acid-functionalmonomer. Examples of active hydrogen-functional monomers include,without limitation, hydroxyl-functional monomers such as hydroxyethylacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate,hydroxypropyl methacrylate, hydroxybutyl acrylates, and hydroxybutylmethacrylates; and carbamate- and urea-functional monomers or monomerswith functional groups that are converted to carbamate or urea groupsafter polymerization such as, without limitation, those disclosed inU.S. Pat. No. 5,866,259, “Primer Coating Compositions ContainingCarbamate-Functional Acrylic Polymers,” the entire disclosure of whichis incorporated herein by reference. Preferably, a sufficient amount ofactive hydrogen-functional monomer is included to produce an equivalentweight of 1000 or less grams per equivalent, more preferably 800 or lessgrams per equivalent, and even more preferably 600 or less grams perequivalent.

[0146] It is preferred that the acrylic polymer preferred for use aspart of compound (II)(a) be dispersed as an anionic dispersion. Examplesof suitable acid-functional monomers include, without limitation,α,β-ethylenically unsaturated monocarboxylic acids containing 3 to 5carbon atoms, α,β-ethylenically unsaturated dicarboxylic acidscontaining 4 to 6 carbon atoms and the anhydrides and monoesters ofthese. Examples include, without limitation, acrylic acid, methacrylicacid, crotonic acid, maleic acid or maleic anhydride, itaconic acid oritaconic anhydride, and so on. A sufficient amount of acid-functionalmonomer is included to produce an acrylic polymer with an acid number ofat least about 1, and preferably the acrylic polymer has an acid numberof from about 1 to about 10.

[0147] In addition to the ethylenically unsaturated monomer having acidfunctionality or used to generate acid functionality in the finishedpolymer, one or more other ethylenically unsaturated monomers areemployed as comonomers in forming the acrylic resins preferably used incompound (II)(a). Examples of such copolymerizable monomers include,without limitation, derivatives of α,β-ethylenically unsaturatedmonocarboxylic acids containing 3 to 5 carbon atoms, including esters,nitriles, or amides of those acids; diesters of α,β-ethylenicallyunsaturated dicarboxylic acids containing 4 to 6 carbon atoms; vinylesters, vinyl ethers, vinyl ketones, vinyl amides, and aromatic orheterocyclic aliphatic vinyl compounds. Representative examples ofacrylic and methacrylic acids, amides and aminoalkyl amides include,without limitation, such compounds as acrylamide,N-(1,1-dimethyl-3-oxobutyl)-acrylamide, N-alkoxy amides such asmethylolamides; N-alkoxy acrylamides such as n-butoxy acrylamide;N-aminoalkyl acrylamides or methacrylamides such asaminomethylacrylamide, 1-aminoethyl-2-acrylamide,1-aminopropyl-2-acrylamide, 1-aminopropyl-2-methacrylamide,N-1-(N-butylamino)propyl-(3)-acrylamide and 1-aminohexyl-(6)-acrylamideand 1-(N,N-dimethylamino)-ethyl-(2)-methacrylamide,1-(N,N,-dimethylamino)-propyl-(3)-acrylamide and1-(N,N-dimethylamino)-hexyl-(6)-methacrylamide.

[0148] Representative examples of esters of acrylic, methacrylic, andcrotonic acids include, without limitation, those esters from reactionwith saturated aliphatic and cycloaliphatic alcohols containing 1 to 20carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl,isobutyl, tert-butyl, 2-ethylhexyl, lauryl, stearyl, cyclohexyl,trimethylcyclohexyl, tetrahydrofurfuryl, stearyl, sulfoethyl, andisobornyl acrylates, methacrylates, and crotonates; and polyalkyleneglycol acrylates and methacrylates.

[0149] Representative examples of other ethylenically unsaturatedpolymerizable monomers include, without limitation, such compounds asfumaric, maleic, and itaconic anhydrides, monoesters, and diesters.Polyfunctional monomers may also be included to provide a partiallycrosslinked acrylic dispersion. Examples of polyfunctional compoundsinclude, without limitation, ethylene glycol diacrylate, ethylene glycoldimethyacrylate, triethylene glycol diacrylate, tetraethylene glycoldimethacrylate, 1,6-hexanediol diacrylate, divinylbenzene,trimethylolpropane triacrylate, and so on.

[0150] Representative examples of vinyl monomers that can becopolymerized include, without limitation, such compounds as vinylacetate, vinyl propionate, vinyl ethers such as vinyl ethyl ether, vinyland vinylidene halides, and vinyl ethyl ketone. Representative examplesof aromatic or heterocyclic aliphatic vinyl compounds include, withoutlimitation, such compounds as styrene, α-methyl styrene, vinyl toluene,tert-butyl styrene, and 2-vinyl pyrrolidone.

[0151] After polymerization, the acid functionality is salted,preferably with an alkali or base, preferably an amine. Example ofsuitable salting materials include, without limitation, ammonia,monoethanolamine, ethylamine, dimethylamine, diethylamine,triethylamine, propylamine, dipropylamine, isopropylamine,diisopropylamine, triethanolamine, butylamine, dibutylamine,2-ethylhexylamine, ethylenediamine propylenediamine, ethylethanolamine,dimethylethanolamine, diethylethanolamine, 2-amino-2-methylpropanol, andmorpholine. Preferred salting materials include 2-amino-2-methylpropanoland dimethylethanolamine.

[0152] The acrylic polymers preferably used in most preferred compound(I)(a) may be prepared as solutions in an organic solvent medium,preferably selected from water-soluble or water-miscible organicsolvents, and then dispersed into water. After dispersion into water,the organic solvent can be distilled from the aqueous dispersion oremulsion.

[0153] In a preferred method, the acrylic polymer preferred for use ascompound (II)(a) is provided by emulsion polymerization. Preferably, anonionic or an anionic surfactant is used for the emulsionpolymerization. Suitable surfactants include, without limitation,polyoxyethylenenonylphenyl ethers, polyoxyethylenealkylallyl ethersulfuric acid esters, amino and alkali salts of dodecylbenzenesulfonicacid such as the dimethylethanolamine salt of dodecylbenzenesulfonicacid and sodium dodecylbenzenesulfonic acid, and sodiumdioctylsulfosuccinate.

[0154] The polymerization typically proceeds by free radicalpolymerization. The free radical source is typically supplied by a redoxinitiator or by an organic peroxide or azo compound. Useful initiatorsinclude, without limitation, ammonium peroxydisulfate, potassiumperoxydisulfate, sodium metabisulfite, hydrogen peroxide, t-butylhydroperoxide, dilauryl peroxide, t-butyl peroxybenzoate,2,2′-azobis(isobutyronitrile), and redox initiators such as ammoniumperoxydisulfate and sodium metabisulfite with ferrous ammonium sulfate.Optionally, a chain transfer agent may be used. Typical chain transferagents include mercaptans such as octyl mercaptan, n- or tert-dodecylmercaptan, thiosalicylic acid, mercaptoacetic acid, and mercaptoethanol;halogenated compounds; and dimeric alpha-methyl styrene.

[0155] Acrylic polymers prepared by emulsion polymerization can haveweight average molecular weights of one million or more. The weightaverage molecular weight of the acrylic dispersion is preferably fromabout 5,000 to about 5,000,000, more preferably from about 7500 to about500,000, and even more preferably from about 10,000 to about 50,000. Ifprepared by solution polymerization and then dispersed in water, theacrylic polymer will generally have a number average molecular weight offrom about 5000 to about 60,000. The molecular weight can be determinedby gel permeation chromatography using a polystyrene standard or otherknown methods.

[0156] The theoretical glass transition temperature of the acrylicpolymer can be adjusted according to methods well-known in the artthrough selection and apportionment of the comonomers. The acrylicpolymer has a glass transition temperature that is at least about 20° C.higher than the glass transition temperature of polyurethane resin.Preferably, the acrylic polymer has a glass transition temperature thatis at least about 40° C. higher, more preferably about 50° C. higher,than the glass transition temperature of polyurethane resin. In apreferred embodiment, the theoretical T_(g) of the acrylic polymer isbetween about −30° C. and 80° C., more preferably between about −20° C.and 40° C.

[0157] In the most preferred compound (II)(a), the polyurethane polymerwill be included in compound (II)(a) in an amount of at least about 40%by weight, preferably at least about 50% by weight, based on the totalnonvolatile weight of compound (II)(a). The polyurethane polymer may beincluded in compound (II)(a) in an amount of up to about 98% by weight,preferably up to about 80% by weight, based on the total nonvolatileweight of compound (II)(a). It is preferred to include from about 50% byweight to about 75% by weight, and even more preferred to include fromabout 65% by weight to about 75% by weight, of the polyurethane polymer,based on the total nonvolatile weight of compound (II)(a).

[0158] Curable coating composition (I) will further comprise a curingagent (b). Curing agent (b) is a compound having a plurality offunctional groups that are reactive with the active hydrogen-containinggroups on compound (a). Such reactive groups include active methylol ormethylalkoxy groups, isocyanate groups, siloxane groups, cycliccarbonate groups, and anhydride groups. Examples of compounds suitalblefor use as curing agent (II)(b) include aminoplast resins,phenol/formaldehyde adducts, blocked isocyanate curing agents,tris(alkoxy carbonylamino) triazines (available from Cytec Industriesunder the tradename TACT) and mixtures thereof. Aminoplast resins andphenol/formaldehyde adducts are most preferred, with blocked isocyanatesbeing disfavored. Suitable aminoplast resins are amine/aldehydecondensates, preferably at least partially etherified, and mostpreferably fully etherified. Melamine and urea are preferred amines, butother triazines, triazoles, diazines, guanidines, or guanamines may alsobe used to prepare the alkylated amine/aldehyde aminoplast resinscrosslinking agents. The aminoplast resins are preferablyamine/formaldehyde condensates, although other aldehydes, such asacetaldehyde, crotonaldehyde, and benzaldehyde, may be used.Non-limiting examples of preferred aminoplast resins include monomericor polymeric melamine formaldehyde resins, including melamine resinsthat are partially or fully alkylated using alcohols that preferablyhave one to six, more preferably one to four, carbon atoms, such ashexamethoxy methylated melamine; urea-formaldehyde resins includingmethylol ureas and siloxy ureas such as butylated urea formaldehyderesin, alkylated benzoguanimines, guanyl ureas, guanidines,biguanidines, polyguanidines, and the like. Monomeric melamineformaldehyde resins are particularly preferred. The preferred alkylatedmelamine formaldehyde resins are water miscible or water soluble.

[0159] The curing agent (II)(b) may generally be present in curablecoating composition in an amount of from 1 to 50% by weight, preferablyfrom about 2% by weight to about 30% by weight, more preferably fromabout 5% by weight to about 20% by weight, and particularly preferablyabout 5% to about 15% by weight of the total nonvolatile weight ofcompound (II)(a) and curing agent (II)(b).

[0160] It is a necessary aspect of the instant invention that the curingagents of the respective coatings (I) and (II) be essentiallyinterchangeable. That is, curing agent (I) must be such that it wouldcure curable coating composition (II) under the applied cure conditions,if it were substitued in place of curing agent (II). Similarly, curingagent (II) must be such that it would cure curable coating composition(I) under the applied cure conditions, if it were substituted in placeof curing agent (I). While it is not necessary that curing agent (I) andcuring agent (II) be identical, it is preferred that they possess thesame reactive groups. Most preferably, the curing agents (I) and (II)will be the same. Accordingly, curable coating compositions (I) and (II)must be selected so as to satisfy this requirement.

[0161] In a preferred embodiment, the curable coating compositions (I)and (II) will both further comprise a catalyst (c) for the reactionbetween reactive compound (a) and curing agent (b), wherein the catalyst(I)(c) is also a catalyst for the reaction between reactive compound(II)(a) and curing agent (II)(b), and the catalyst (II)(c) is also acatalyst for the reaction between reactive compound (I)(a) and curingagent (I)(b). The phrase “is also a catalyst for” is meant to indicatethat said catalyst changes the speed of the other reaction as well asthe reaction for which it is originally intended to be catalytic. Thatis, catalyst (I)(a) will, under the applied curing conditions, changethe speed of the reaction (I)(a)+(I)(b), as well as change the speed ofthe reaction (II)(a)+(II)(b). Likewise, catalyst (II)(c) will, under theapplied curing conditions, change the speed of the reaction(II)(a)+(II)(b), as well as change the speed of the reaction(I)(a)+(I)(b).

[0162] The curable coating composition (II) may thus contain one or morecatalyst (s) to facilitate the reaction between compound (a) and curingagent (b). For example, a strong acid catalyst may be utilized toenhance the cure reaction. It will be appreciated that such catalystsmay be blocked or unblocked. Such catalysts are well-known in the artand include, for example, p-toluenesulfonic acid, dinonylnaphthalenedisulfonic acid, dodecylbenzenesulfonic acid, phenyl acid phosphate,monobutyl maleate, butyl phosphate, and hydroxy phosphate ester. Thenecessary acid to catalyze the desired reaction of compound (II)(a) andcuring agent (II) may also be provided by the acid functional groups ofcompound (II)(a). Other catalysts useful in the composition of theinvention include Lewis acids, zinc salts, and tin salts. IllustrativeLewis acids or zinc salts are zinc nitrate, zinc acetate, bismuthoctoate, dibutyltin dilaurate, and the like. Such catalysts willtypically be used in an amount of from 0.1 to 3.0 weight percent, basedon the resin solids, preferably from 0.5 to 2.0 weight percent, based onthe resin solids. A most preferred catalyst for use in curable coatingcomposition (II) of the invention is an acid catalyst such as a DDBSA,either blocked or unblocked.

[0163] Curable coating composition (II) may be a solvent or aqueousbased coating, including but not limited to, an aqueous powder slurrycomposition. Also, the coating composition (II) can be applied withoutsolvent, in the case of a powder coating. However, in many cases, it isdesirable to use a solvent in the coating composition. This solventshould act as a solvent with respect to compound (a) and curing agent(b). In general, depending on the solubility characteristics ofcomponents (a) and (b), the solvent can be any organic solvent and/orwater. In one preferred embodiment, the solvent is a polar organicsolvent. More preferably, the solvent is a polar aliphatic solvents orpolar aromatic solvents. Still more preferably, the solvent is a ketone,ester, acetate, aprotic amide, aprotic sulfoxide, or aprotic amine.Examples of useful solvents include methyl ethyl ketone, methyl isobutylketone, amyl acetate, ethylene glycol butyl ether-acetate, propyleneglycol monomethyl ether acetate, xylene, N-methylpyrrolidone, or blendsof aromatic hydrocarbons. In another embodiment, the solvent can bewater or a mixture of water with co-solvents.

[0164] In some preferred embodiments, curable composition (II) will bean aqueous coating composition. Besides water, the aqueous medium ofcurable coating composition (II) may also contain a coalescing solvent.Useful coalescing solvents include hydrocarbons, alcohols, esters,ethers and ketones. The preferred coalescing solvents include alcohols,polyols and ketones. Specific coalescing solvents include monobutyl andmonohexyl ethers of ethylene glycol, and phenyl ether of propylene,ethylene glycol butyl ether, ethyleneglycol dimethyl ether, or mixturesthereof. A small amount of a water-immiscible organic solvent such asxylene, toluene, methyl isobutyl ketone or 2-ethylhexanol may be addedto the mixture of water and the water-miscible organic solvent. Theamount of coalescing solvent is not unduly critical and is generallybetween about 0 to 15 percent by weight, preferably about 0.5 to 5percent by weight based on total weight of the resin solids.

[0165] In a particularly most preferred embodiment, the curable coatingcomposition (II) will have a very low content of volatile organicsolvent. In an especially preferred embodiment, the curable coatingcomposition (II) will be an aqueous powder slurry composition. In suchan embodiment, the polyurethane dispersion used as part of compound(II)(a) will be preferably prepared as a solvent free or substantiallysolvent free dispersion. By “substantially solvent free” it is meantthat the dispersion has a volatile organic content of less than about 5%by weight of the primer composition. The acrylic dispersion also used incompound (II)(a) will also be preferably solvent free or substantiallysolvent free dispersion. In this most preferred embodiment, the curablecoating composition (II) will preferably have a VOC of less than about1.5, more preferably less than about 1.3, and even more preferably lessthan about 0.7. The VOC of a coating composition is typically measuredusing ASTM D3960.

[0166] The curable coating composition (II) may further contain pigmentssuch as are commonly used in the art, such as color pigments, corrosioninhibiting pigments, conductive pigments, and filler pigments. Suitableexamples include, without limitation, titanium dioxide, metal oxidessuch as ferric oxide, carbon black, silicates such as aluminum silicateand basic lead silicate, sulfates such as precipitated barium sulfate,molybdates such as aluminum phosphomolybdate, chromates such asstrontium chromate and lead chromate, phosphates, silicas, and mixturesthereof. The pigment-to-resin weight ratio can be important and shouldbe preferably less than 50:100, more preferably less than 40:100, andusually about 10 to 30:100.

[0167] In a most preferred embodiment, the curable coating composition(II) will be tinted so as to have a color which corresponds to asubsquently applied basecoat. The use of a tinted primer or sealerallows for the application of lower basecoat film builds.

[0168] Curable coating composition (II) can contain optional ingredientssuch as wetting agents, surfactants, defoamers, antioxidants, UVabsorbers, light stabilizers, and so forth. Examples of surfactants andwetting agents include alkyl imidazolines such as those available fromCiba-Geigy Industrial Chemicals as Amine C®, acetylenic alcoholsavailable from Air Products and Chemicals as Surfynol®104. Theseoptional ingredients, when present, constitute from about 0 to 20percent by weight of resin solids, and preferably from 0.1 to 1.0percent by weight of resin solids. Plasticizers are optional ingredientsbecause they promote flow. Examples are high boiling water immisciblematerials such as polyalkylene polyols, such as polypropylene polyols orethylene or propylene oxide adducts of nonyl phenols or bisphenol A.Plasticizers can be used and if so are usually used at levels of about 0to 15 percent by weight resin solids.

[0169] After application of curable coating composition (II) ontosubstantially uncured or wet curable coating composition (I), thewet-on-wet composite of curable coating composition (I) and curablecoating composition (II) may and most preferably will be cured at anelevated temperature, depending upon the nature of particular baseresins. In general, depending upon the nature of the compositionsutilized as curable coating compositions (I) and (II), the wet-on-wetcomposite will be cured by exposure to temperatures in the range of from100 to 200° C., preferably from 120 to 180° C., and most preferably from135 to 155° C. However, it will be appreciated that other cureconditions such as exposure to IR and blackwall radiation may also beused to crosslink the two curable coating compositions.

[0170] Although prior art cathodic electrodeposition coating typicallycure at approximately 20 minutes at 176° C. (metal temperature), thepreferred anodic and cathodic curable coating compositions (I) discussedabove generally cure at lower temperatures. The preferred anodic curablecoating composition (I) will generally cure upon approximately 30 to 15minutes, most preferably 20 minutes, exposure to 135 ° C., mostpreferably 110° C. In the most preferred embodiment, the most preferredcathodic electrodeposition coating composition discussed above will beused as curable coating composition (I) and will cure at 30 to 15minutes, preferably 20 minutes, at 154° C. or less (metal temperature),preferably at 20 minutes at 135° C. (metal temperature). Therefore, inthe most preferred embodiment of the invention, the wet-on-wet compositeof both curable coating composition (I) and curable coating composition(II) will be cured at a temperature of from 120 to 180° C., mostpreferably from 135 to 155° C., for a time of from 5 to 40 minutes, mostpreferably from 15 to 25 minutes.

EXAMPLE 1 Preparation of a Polymer (A) for Use as Compound (I)(a) Part(i) Preparation of Polymer Intermediate (A′) and Reactive Additive (Ac′)

[0171] To a 1 liter round bottom 4-neck flask set up with an additionfunnel, condenser, temperature probe and mixing shaft was added 333.5grams (1.5 moles) of isophorone diisocyanate (IPDI), 0.5 grams ofdibutyltindilaurate and 152.0 grams of MIBK (methyl isobutyl ketone-urethane grade/dry). A total of 232.1 grams (1.95 moles) ofhydroxypropyl carbamate (HPC) was added to the addition funnel. The HPCfrom the addition funnel was added to the flask at such a rate that thetemperature was maintained at 34° C. to 40° C. The temperature was thenmaintained at 40° C. for three hours and the NCO content was verified bytitration to be 682 grams product/eq NCO. (539 g solid/eq NCO). Thefinal product was 78.8% solid content and contained 2 moles of carbamatefunctional intermediate (A′) to 1 mole of “in-situ” generated carbamatereactive intermediate (Ac′).

Part (ii) Preparation of Polymer (A)

[0172] To a 3000 ml flask equipped with a mixer, condenser andtemperature probe were added 376.0 g diglycidyl ether of bisphenol A (1mole at EEW=188), 153.9 g bisphenol A (0.675 moles), 52.4 gdodecylphenol (0.2 moles) and 30.7 g xylene. The reaction was heated to125° C. and 0.4 g of triphenylphosphine were added. The reaction wasexothermic and the temperature was maintained at 150° C. for 1 hour andthe weight per epoxy was confirmed to be 1263 g solid/eq. epoxy. Thebatch was cooled from 150° C. to 95° C. by the addition of 100.0 gramsof MIBK. At 95° C., 300.0 g of the carbamate functional intermediatefrom Ex 1, part (i) above was added. The reaction temperature wasmaintained at 95° C. for 2.5 hours and the loss of isocyanate andcompletion of the graft reaction was confirmed by titration. At 95° C.,73.8 grams of a mixture of 27.6 grams (0.31 moles) ofdimethylethanolamine, 37.8 grams of lactic acid (86%) and 36.0 grams ofwater were added. The temperature of the reaction was then maintained at95° C. for 3 hours. The resin was diluted with 41.5 grams of propyleneglycol phenyl ether and 41.5 grams ethylene glycol butyl ether andcooled to 60° C. The resin was 75% solids and had a molecular weight(Mw) of 4654 as measured by by gel permeation chromatography. The resinhas a carbamate equivalent weight of 1079 grams solid resin/equivalentcarbamate. The meq Quat/gram NV is 0.352.

EXAMPLE 2 Preparation of a Curable Coating Composition (I)

[0173] 500.0 grams of the reaction product of Example 1 above, 230.9grams of a butylated melamine resin (Monsanto Resimine 7539), 54.6 gramsof the reactive additive (C) of Example 1, 23.0 grams of ethylene glycolbutyl ether, 23.0 grams of propylene glycol phenyl ether were added to aone gallon vessel. This was mixed until homogenous. 8.3 grams of bismuthoctocate catalyst and 5.5 grams of zinc nitrate catalyst were thenadded. A total of 1109 grams deionized water was added in portions withgood mixing. The resulting emulsion had a solids content of 25%.Additonal DI water was added to reduced the viscosity and the organicsolvent was allowed to strip from the stirred emulsion for one day.After one day, the stripped emulsion had a viscosity of 35 cps and was23% solids. The pH was 5.2 and the conductivity was 1231 micromhos. Theemulsion had a particle size of 1.52 microns. The meq Quat content was0.29 meq quaternary ammonium sites/gram solid.

EXAMPLES Example 3 Preparation of a Cathodic Electrocoat Bath Using theCationic Curable Coating Composition (I) Part (i) Preparation of a GreyPigment Paste

[0174] To a tank were added the following materials in order, 2,624.2parts of deionized water and 1,879.60 parts of a urethane epoxy resinsolution prepared in accordance with Example II of U.S. Pat. No.4,007,154. The materials were mixed for a minimum of ten minutes and thefollowing added under low agitiation, 38.50 parts of K-2000 additive,commercially available from Byk-Chemie, 127.20 parts of a black pigment,217.9 parts of dibutyl tin oxide and 254.2 parts of lead silicate. Themixing speed was increased to high and the paste mixed for a minimum often minutes. 90.8 parts of clay-aluminum silicate was added. High speedmixing was maintained while 4,213 parts of white TiO₂ were added. Thepaste was mixed for a minimum of 45 minutes. Deionized water was addedto obtain a viscosity of 75-85 Kreb units.

Part (ii) Preparation of a Cathodic Electrocoat Bath

[0175] To a gallon vessel were added 2391 grams of principal emulsion ofExample 2 above and 150.0 grams of the grey pigment paste from Ex 3,part (i) above. The bath was diluted with 709 grams DI water. The bathhad a pigment/binder ratio of 0.12 and a solids content of 20%. The bathwas mixed for 2 hours in an open vessel. The bath had a pH of 5.4 and aconductivity of 642 nmicromhos.

EXAMPLE 4 Preparation of a Curable Coating Composition (II)

[0176] A primer composition was prepared by first mixing together 17.51parts by weight of BAYHYDROL 140 AQ polyurethane dispersion (about 40%nonvolatile, 59% water, and 1% toluene, glass transition temperature ofabout −45° C., pH of about 6.0 to about 7.5, weight average molecularweight of about 25,000, anionic Desmodur W/1,6-hexaamethylenediisocyanate/polyester polyol-based polyurethane, available from BayerCorporation, Pittsburgh, Pa.), 16.27 parts by weight of an emulsion ofan acrylic polymer (glass transition temperature of 20° C., nonvolatilecontent of about 41% in water, acid number of about 8 mg KOH/gnonvolatile, hydroxyl equivalent weight of 510, salted with2-amino-2-methylpropanol to a pH of about 6 to 7), 20.9 parts deionizedwater, and 40.89 parts by weight of pigment paste (63% by weightnonvolatile in water, nonvolatiles are 33.1% by weight of BAYHYDROL 140AQ polyurethane resin, 33.1% by weight of titanium dioxide, 33.1% byweight of barium sulfate extender, and the balance carbon black, groundon a horizontal mill to a fineness of 6 microns). To this mixture wereadded 2.71 parts by weight of RESIMENE 747 (a melamine formaldehyderesin available from Solutia, St. Louis, Mo.) and 0.27 parts by weightof ABEX EP 110 (anionic surfactant available from Rhodia). A total of1.39 parts by weight of an additive package (defoamer, wetting agent,and thickener) was then added. Finally, the pH of the primer compositionwas adjusted to about 8.0 with 2-amino-2-methylpropanol.

[0177] The measured volatile organic content of the primer compositionwas 0.24 pounds per gallon. The primer composition had a nonvolatilecontent of 42% by weight. The primer composition was adjusted beforespray application with deionized water to a viscosity of 75 to 110centipoise.

EXAMPLE 5 Deposition of Cathodic Electrocoat Coating Composition (I)

[0178] Using a DC rectifier a 4″×12″ steel panels were coated viacathodic electrodeposition with the cathodic electrocoat bath of Example3. The set voltage was 50 volts. The amps were set at 0.8 amps and thedeposition time was 2.2 minutes. The bath temperature was 90° F. Thetarget film build was 0.5 mils. The resulting panels were flashed for 5minutes at 100 degrees C. After completion of the flash, the panels werethen spray applied with the curable coating composition of Example 4.The resulting multilayer coating was then baked for 30 minutes at 150degrees C. The target film build for curable coating composition (II)was 1.0 mils for a total dry film build of 1.5 mils. The 20°/60° glosswas respectively 15.8 and 60.1. The panel had some wrinkle and pop.Crosshatch adhesion was a pass. The multilayer film had less than 0.1%paint loss/excellent on the 1200 ml shot/chipping test.

I claim:
 1. A method of making a cured multilayer coating, the methodcomprising applying by electrophoretic deposition a first curablecoating composition (I) to a substrate, the first curable coatingcomposition (I) comprising, (a) a compound comprising one or more activehydrogen-containing groups, and (b) a curing agent comprising one ormore groups reactive with active hydrogen-containing groups, applying asecond curable coating composition (II) to the applied first curablecoating composition (I) while the applied first curable coatingcomposition is in an uncured state, the second curable composition (II)comprising (a) a compound comprising one or more activehydrogen-containing groups, and (b) a curing agent comprising one ormore groups reactive with active hydrogen-containing groups, andsubjecting the applied first and second curable coating compositions toconditions sufficient to cause curing of both compositions, whereincuring agent (I)(b) is reactive with compound (II)(a) and curing agent(II)(b) is reactive with compound (I)(a) under the applied cureconditions.
 2. The method of claim 1 wherein the first curable coatingcomposition (I) further comprises (c) a catalyst for the reactionbetween reactive compound (I)(a) and curing agent (I)(b), and the secondcurable coating composition (II) further comprises (c) a catalyst forthe reaction between reactive compound (II)(a) and curing agent (II)(b).3. The method of claim 2 wherein the catalyst (I)(c) is also a catalystfor the reaction between reactive compound (II)(a) and curing agent(II)(b), and the catalyst (II)(c) is also a catalyst for the reactionbetween reactive compound (I)(a) and curing agent (I)(b).
 4. The methodof claim 1 wherein subjecting the applied first and second curablecoating compositions to conditions sufficient to cause curing of bothcompositions occurs simultaneously.
 5. The method of claim 4 wherein theapplied first and second curable coating compositions are cured by beingsubjected to a temperature of 350 degrees C or less for 30 minutes orless.
 6. The method of claim 1 wherein curing agent (I)(b) is free ofisocyanate groups.
 7. The method of claim 6 wherein curing agent (I)(b)is free of blocked isocyanate groups.
 8. The method of claim 1 whereincuring agent (I)(b) is aminoplast resin.
 9. The method of claim 1wherein curing agent (II)(b) is aminoplast resin.
 10. The method ofclaim 8 wherein curing agent (II)(b) is aminoplast resin.
 11. The methodof claim 1 wherein the first curable coating composition (I) is ananodic electrocoat coating composition.
 12. The method of claim 1wherein the first curable coating composition (I) is a cathodicelectrocoat coating composition.
 13. The method of claim 1 wherein thesecond curable coating composition (I) is a waterborn coatingcomposition.
 14. A multilayer film composition comprising (I) a firstfilm resulting from the curing of a first curable coating composition(I) comprising (a) a compound comprising one or more activehydrogen-containing groups, and (b) a curing agent comprising one ormore groups reactive with active hydrogen-containing groups, and (II) asecond film resulting from the curing of a a second curable coatingcomposition (II) comprising (a) a compound comprising one or more activehydrogen-containing groups, and (b) a curing agent comprising one ormore groups reactive with active hydrogen-containing groups, wherein(1.) the second curable coating composition (II) was applied to thefirst curable coating composition (I) while the first curable coatingcomposition (I) was in an uncured state, and (2.) curing agent (I)(b)was reactive with compound (II)(a) and curing agent (II)(b) was reactivewith compound (I)(a) in the conditions in which the first and secondcurable coating compositions were cured.